66 DIPTERA 
entirely connate, the last joint elongate conical, with à very slender elongate bare single-jointed terminal 
arista; mouthparts very short, haustellate, the palpi scarcely projecting and hairy ; ocellar triangle small, 
ocellar bristles reaching halfway to the antennze, two pairs of vertical bristles of similar length. "Thorax 
less than half as long as the abdomen and broader than the head, with very fine seriate pubescence, 
lateral bristles long but hair-like, an ascending row of three notopleurals, one supraalar, one postalar, 
one prescutellar and several scutellars present. Abdomen cylindrical, pygidium small, distorted, asym- 
metrical, the valves with slender ribbon-like processes; terminal segments of the female usually prolonged 
to an ensiform chitinized ovipositor. Legs slender, hairy, cox short, the front coxe slightly the longest, 
femora without bristles, middle tibiae with several sets of long bristles. Wings elongate, anal angle 
prominent, rounded rectangular, basal bristle of the costa present, costa stopping beyond the third vein, 
pubescence of the wing-membrane coarse, auxiliary vein rudimentary, lying closeto the first vein, which 
terminates at the outer fourth of the wing, third vein simple, its pedicel long, discal cell emitting two 
unforked veins which are the fifth and sixth longitudinals, only a spur of the fourth vein sometimes 
distinguishable beyond the discal cell, basal cells large, the first basal narrower than the second, anal 
cell shorter than the second basal, obliquely truncate by its reflexed straight crossvein. 
Type species : L. /lavipes, Meigen (Pl. 8, Fig. 19), the only species given in the original 
description, and which is synonymous with ruficollis Meigen. The habits of the species of this genus are 
unknown, except that the adults occur in open and rather shady spots in woods near streams or lakes. 
Most of the species, like ruficollis, borealis, nigripes, disparilis and compta are not clearly limited, and often 
specimens can be found on the borderland between species, making identification difficult at times. 
This is due to the variable color within the species and the stereotyped habitus of the genus. — SPhenoptera, 
however, departs from the others and several times it has been suggested that this species be removed 
from Lefíofesa. lt is peculiar in several characters, and in many ways is more closely related to the 
South American Hoflofesa than to Leffopesa. This species has here been removed under the generic 
name Leftometofiella 
TABLE FOR THE SEPARATION OF THE NEARCTIC SPECIES OF LEPTOPEZA 
1. Thorax devoid of pubescence, lightly pollinose, scutellum with only two 
bristles; antenna elongate, arista white, outer joint six times as long 
as broad and three times as long as the inner joint; no ovipositor ; 
wings strongly infumated; mouthparts black. . . . . . . . L. ANTENNALIS, OY. Sp. (1). 
Thorax shining, with short but evident pubescence, scutellum with 
more than two bristles; antennz much shorter, the arista black; a 
long ensiform ovipositor developed; wings clear. . . . "EQUNCAR DU pop. UT 
2. Mouthparts black; antennze black; hind femora and tibize hel black, 
especially in the male . . . . . . . V PN dlc. uc. VR DN ULT EE 
(1) Leptopeza antennalis, nov. sp. — Length 3.5 mm. Black, thorax almost devoid of pubescence, lightly 
pollinose, scutellum with only two bristles; antennze elongate, the outer joint six times as long as wide and three times as 
long as the basal joint, arista yellow ; no ovipositor, Upper facets of male large, occiput with brownish pollen, mouthparts 
black, arista about one-third longer than the black antennze, the outer antennal joint narrow and tapering. Hairs of the 
mesonotum and scutellum very sparse and microscopic. Abdomen shining, hairs of the first ventral long dense and pale, 
pygidium small but open, the middle valves strongly forcipate. Cox: yellow, base of legs yellow, becoming progressively 
darker distally to the piceous tarsi, the hind legs darkest. Halteres yellow (Q) or with black knob (G'). Wings strongly 
infumated, no stigma. 
Six specimens; Washington, D. C., August 17, 1913, taken by the author near Chain Bridge on the Potomac River. 
It is strange that this very distinct species was not discovered earlier by the many entomologists who have collected in this 
locality. 
